<!doctype html>
<html lang="en">
  <head>
    <title>Title</title>
    <!-- Required meta tags -->
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

    <!-- Bootstrap CSS -->
    <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
  </head>
  <style>
    .row{
          border: 1px solid green;
      }
    .row div{
          border: 1px solid black;
      }
  </style>
  <body>
    <div class="container-fluid" style="border: 2px solid red;">
       <div class="row">
            <div class="col-lg-6 col-md-6 col-sm-6">
                col-6
            </div>
            <div class="col-lg-6 col-md-6 col-sm-6">
                col-6
            </div>
       </div> 
       <div class="row">
            <div class="col-lg-4 col-md-4">
                col-4
            </div>
            <div class="col-lg-6 col-md-6">
                <div class="row">
                    <div class="col-sm-6">
                        col-6
                    </div>
                    <div class="col-sm-6">
                        col-6
                    </div>
                </div>
                <div class="row"></div>
                    第二行
            </div>
            <div class="col-lg-2 col-md-2">
                col-2
            </div>
       </div>
       <div class="row">
            <div class="col-md-12">
                <div class="row">
                    <div class="col-lg-4 col-md-4 col-sm-4 ">   
                        col-4
                    </div>
                    <div class="col-lg-8 col-md-8 col-sm-8 ">
                        col-8
                    </div>
                    
                </div>
                <div class="row">
                   <div class="col-lg-3 col-md-3 col-sm-3 ">
                        col-3
                   </div> 
                   <div class="col-lg-4 col-md-4 col-sm-4 ">
                        col-4
                    </div> 
                    <div class="col-lg-7 col-md-7 col-sm-7 ">
                        col-7
                    </div> 
                </div>
                
                <div class="row">
                    <div class="col-md-2">
                        col-2
                    </div>
                    <div class="offset-md-3 col-md-5">
                        col-5
                    </div>
                </div>
                
            </div>
            
       </div>
    </div>


    <!-- Optional JavaScript -->
    <!-- jQuery first, then Popper.js, then Bootstrap JS -->
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
    <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
  </body>
</html>